Heat exchanger method and apparatus



R. P. ADAMS HEAT EXCHANGER METHOD AND APPARATUS Oct. 13, 1964 Filed Oct. 19, 1961 RENAQD P. AoAMs ATTORNEYS United States Patent 3,152,753 WAT EXCHANGER METHOD AND APPARATUS Renard P. Adams, 87 Nottingham Terrace, Buffalo 16, NY. Fiied Oct. 19, 1961, Ser. No. 146,147 8 Claims. (Qt. 230-208) The present invention relates to a heat exchanger method and apparatus and more particularly to such a system for use with gas compressors and the like.

It is an object of the present invention to eliminate the need for an intercooler between the first and second stage of an air compressor system and to thereby eliminate the expense of the intercooler.

It is another object of the present invention to increase the over-all performance of an air compressor system by using all of the effective heat from the discharge air of the low pressure cylinder of an air compressor to reheat the cooled air discharged from the high pressure stage of an air compressor.

It is another object of the present invention to provide a heat exchanger system used in connection with an air compressor to provide an ultimate user with more actual physical volume of compressed air for useful work than ispossible from conventional systems now in use utilizing the standard aftercooler.

It is another object of the present invention to provide a heat exchanger method and apparatus in which the actual pounds of air involved throughout the entire apparatus will remain the same, but the physical volume of air in its expanded state will do more useful work in all kinds of air using or consuming apparatus than is possible with cold air discharged from a standard aftercooler installation.

Heretofore, it has been customary in a heat exchange system used with a two-stage air compressor apparatus, to provide an intercooler which reduces the temperature of the air discharged from the low pressure cylinder or first stage of the air compressor back tothe temperature of the intake airentering the low presure cylinder. The purpose of the intercooler disposed bewteen the two stages of the air compressor is that of reducing the volume of the compressed air back to a point equivalent to or approaching the air intake temperature of the low pressure stage of the compressor so that the physical size of the high pressure cylinder of the compressor can be reduced or properly proportioned to receive this cooled air. It the air is not sufiiciently cooled, it follows that the high pressure cylinder of the compressor must be physically larger in order to accommodate the increased physical volume of air which weighs the same amount but is in a greatly expanded condition or state due to the high or advanced temperature. r In such a conventional two-stage system, the high pressure stage discharges at a pressure of approximately 125 .p.s.i.g. or more and. at a temperature of approximately 250 F. This air contains the greater portion of the water vapor which was passed into the, low pressure stage of the compressor, as well as the greater portion of the oil vapor introduced into the system from the lubricating oil required in both cylinders or stages of the compressor. Of course, there is a certain minor percentage of condensed moisture which is removed from the first stage by the intercooler between the stages. However, the volume of water vapor still remaining in the of the cooling water flowed through the aftercooler. The

air discharged from the aftercooler is approximately 10 "ice higher than the available cooling water flowing through the aftercooler which, depending upon the season, is generally between 50 to 70 F. Thus, the aftercooler serves to contract the physical volume of the air discharged from the second or high stage of the air compressor and such volume is in keeping with the temperature at which the compressed air leaves or is discharged from the aftercooler.

In accordance with the present invention, a novel heat exchanger method and apparatus is provided for use with a two-stage air compressor and the like to eliminate the use of the standard intercooler used heretofore in an air compressor system. As previously stated, the compressed air discharged from the low pressure cylinder of a twostage compressor emerges at a temperature of approximately 250 F. and contains a large quantity of water vapor present'in the intake air to the cylinder. This air discharged from the low pressure cylinder is passed through the tube bundle section of a heat exchanger in an indirect heat exchange relationship with air from the second or high pressure stage or cylinder of the air compressor. The air discharged from the first stage. of the air compressor and exiting from the heat exchanger has its temperature lowered from 250 F. down to approximately F. The cooled air from the first stage of the compressor is then directed to a separator and into the intake of the high pressure cylinder where it is compressed to approximately pounds or more p.s.i.g. This pressure, of course, is by way of example only, but is in the approximate or general range of a standard twostage compressor.

The air is then compressed in the second stage or high pressure cylinder of the compressor and accumulates an additional temperature being discharged from the second 2 stage cylinder at approximately 250 F., corresponding to the developed compression ratio of the high pressure cylinder.

This high pressure and high temperature air then passes from the high pressure cylinder through the inside of the tube bundle or tubes of an aftercooler. The after cooler is provided with cooling water flowing around the outside of tube bundle or on the shell side of the aftercooler between 50 and 70 F., depending upon the season. This air from the high pressure stage passes in indirect heat exchange relationship with the cooling water so that the air upon being discharged from the aftercooler is reduced in temperature to within five degrees or more of the available cooling water. This reduction in the temperature of the air being discharged from the second stage of the air compressor will cause the water vapor and any oil vapor therein to precipitate out. The cooled air is then discharged from the aftercooler into a cyclone separator wherein the condensed moisture and oil are removed by conventional cyclonic means.

The cooled air is then passed from the cyclone separator into the shell side of a heat exchanger around the outside or the tubes therein in indirect heat exchange relationship with the hot compressed air flowing through or inside the tubular bundle of the heat exchanger from the first low pressure stage or cylinder of the compressor at approximately'250 F. The passing of the cool air in indirect heat exchange relationship with the hot air here, reduces-the temperature of the hot air from approximately 250 F. tol10 to F. and increasing the temperature of the cooled air to approximately 225 F. The heated air passing through the tube bundle is then discharged to the secondstage of the air compressor. The air discharged from the outlet end of the heat exchanger around the tubes then emerges at a temperature of about 225, which represents about one-third more volume of air in a physical state that is available for useful work.

Thus from the foregoing description and from the following detailed description, various other objects and advantages of the present invention will become apparent when considered in connection with the accompanying drawings forming a part thereof, and in which: I

:FIG. 1 is a flow sheet diagram embodying the present invention, .and

:FIG. 2 isaslight-ly modified embodiment of 'the invention illustratedin .FIG. :1.

Referring to SFIG. .l,'the reierencenumeral It) generally designates a two-stage air compressor having a low pressure cylinder or first stage 11 and a high pressure cylinder or second stage '12. Air to be compressed enters the intake or inlet :opening '13 of the low pressure cylinder at atmospheric pressureand is compressed to approximately 31 psi-g. The compressed air leaves the low pressure cylinder through outlet opening 15 at a temperature of approximately 250 and thereafter flows through a conduit or pipe 16, connected to the outlet 15 at one end and to the inlet 17 of a'heat exchanger generally designated 18. The compressed air entering the heat exchanger 18 flows therein through the inside of a plurality of tubes 1'9 generally forming a tube bundle 2t) and is discharged from the heat exchanger through outlet 21.

In passing through the heat exchanger, the low pressure air passes in indirect heat exchange relationship with cool air :fiowing into heat exchanger 18 through an inlet 22 disposed therein, which cool air' flows through the shell side or portion 23 of the heat exchanger surrounding or disposed around the tube bundle 2t and its individual tubes 19. Staggered bafiie means 24 are provided in the shell section v23 for providing a tortuous path for the cool air to provide a more .efiicient heat transfer between thecool air and the air from low pressure stage passing through the inside of the tubes 19. The cool air entering inlet 22 is preferably at a temperature of approximately 80 more or iless, and is the compressed air discharged :from the second stage or the high pressure cylinder 12 f the compressor. The low pressure air -fromthe first stage of the compressor is discharged from the tubes 19 through outlet 21 at approximately 110 to 130 F. and flows'through conduit 26 connected between discharge 21 and the intake of the high pressure or second stage cylinder 12 of the compressor. Any condensed water vapor in the cooled air that is condensed in passing through heat exchanger '18 is removed and separated by a standard separator 45; disposed in conduit 26 on the downstream side of heat exchanger 18. Thus, the air in emerging from the heat exchanger 18 has its temperature reduced "from approximately 250 down to 110 to 130 so that the volume of the compressed air discharged from the low pressure cylinder 11 is reduced back to a point equavilent to or approaching the air intake volume to the low pressure cylinder 11 so that the size of the second stage or high pressure cylinder 12 may be properly proportioned to receive this cooled air. If the air is not cooled after it is discharged from the low pressure cylinder, the high pressure cylinder 12 must be considerably larger to make'the increased physical volume represented by the same weight of air that is in a greatly expanded condition due to the high temperature.

The air in passing into the high pressure cylinder 12 of the compressor is then compressed to aproximately 125 p.s.i.g. and is discharged from this cylinder at a temperature of approximately 250 F. This air being discharged from the high pressure cylinder contains all of the water vapor which was taken into the atmospheric intake of the low pressure cylinder 11 less the condensation which will take place in the tubes of the heat exchanger 18 through the reduction of temperature from 250 F. to approximately 110 F. Such condensation will be removed in the cyclone separator in the air stream 26. In addition, there will be a quantity of oil vapor resulting from the lubricating oil fed to the air cylinders to provide lubrication for the compressors. This means that there is a considerable amount of moisture and oil in the high pressure gas flowing from the high pressure cylinder 12 through the conducit 27 connected to the discharge or outlet of the high pressure cylinder 12. The opposite end of conduit 27 is connected to an inlet 28 disposed in a second heat exchanger or aftercooler 29 and passes through the inside of a plurality of individual tubes therein and is discharged therefrom through outlet 30.

The aftercooler or second heat exchanger 29 is provided with a cooling water inlet pipe 33 provided with a valve 34 therein and a cooling water discharge pipe 31 provided with a valve 32 therein. The cooling water in passing through pipe 33 flows around the outside of the tube bundle and the individual tubes through which the air flows in heat exchanger 29, so that the water is passed in indirect heat exchange relationship with the hot air flowing through the tubes. The temperature of the water supplied to the heat exchanger 29 is in the range of 50 to 70 F, depending upon the season of the year, and cools the hot air flowing through the tubes down to a temperature of approximately F, or approximately 10 higher than the available cooling water flowing through the aftercooler as it leaves the outlet 30 of the aftercooler. In passing through the aftercooler 29, the hot air entering inlet 28 is cooled so that the reduction in temperature will precipitate out the water and oil vapor. The air emerging from the aftercooler at this lower temperature thereafter flows through the conduit 35 connected to inlet 36 of a cyclone separator 37 and the condensed moisture and oil vapor are discharged into a trap 38, while the cooled air flows through the outlet 39 of the separator into the inlet 22 of the first heat exchanger 18 to which the outlet 39 is connected.

The air from the second stage or high pressure cylinder 12 thereafter flows through the shell 23 of the heat exchanger 18 as described hereinbefore, and is discharged from the outlet '40 in heat exchanger 18 at a temperature of approximately 225 R, which represents about one-third more volume in a physical state than would have been possible from the use of a common aftercooler which is currently and regularly used for the purpose of condensing oil and water in a two-stage air compressor system.

Through the over-all performance in the heat exchange system of the present invention, the efiiciency is increased since all of the effective heat in the discharged air from the low pressure cylinder 11 is used in the heat exchanger 18 to reheat the cooled air passing therethrough from the discharge outlet of the high pressure cylinder 12, and an ultimate user of the compressed air is provided with more actual physical volume of compressed air for useful work than is possible from a standard system using the conventional aftercooler.

It is also apparent that the actual pounds of air flowing through the entire system remains the same, but the physical volume in its expanded state can do more useful work than is possible with the current air emerging from a conventional two-stage air compressor system with a conventional aftercooler.

The embodiment of the invention shown in FIG. 2 is substantially the same in structure as that shown in FIG. 1, except that a small heat exchanger unit 42 having an inlet 43 and an outlet 44 is disposed in conduit 26 between the discharge 21 of the heat exchanger 18 and the inlet to the high pressure cylinder 12, and upstream of separator 48. The heat exchanger 42 is provided with a cooling water inlet pipe 45 and a cooling Water discharge pipe 46 for passing cooling water around the outside of a tube bundle disposed therein.

The cooled gas being discharged from the discharge outlet 21 of the heat exchanger 18 passes'through inlet 43 through the inside of the tubes disposed therein, while the cooling water passes through the shell section m ne who 4 of the heat exchanger 42 around the outside of the tubes therein, to provide cooling water for passing in indirect heat exchange relationship with the air flowing through the tubes. The air being discharged through outlet 44 of the heat exchanger 42 has 'its temperature reduced from the intake temperature'of 110 to 130 back to within of the cooling Water so that the temperature of the air leaving the discharge outlet 44 is approximately 90 to 100 F., so that this air Will be in a more compressed state and enter in physical volume into the controlled volume of the highpressure cylinder 12. The separator 48, similar to separator .37, is disposed downstream of heat exchanger 42 in conduit 26 in the embodiment of FIG. 2, to remove moisture that may be condensed in heat exchanger 18 together with the additional moisture Which Will be condensed in heat exchanger 42.

This embodiment of the invention is a simple heat exchange problem that may develop where the temperature of the air coming out of the tubes of the heat exchanger 13 and discharged to the intake connection of the second stage cylinder 12 may be at a temperature to make the same cylinder in present practice completely usable where a standard air compressor system has al-v ready been installed. Thus, this embodiment of the invention makes it readily adaptable to installations in the field.

Inasmuch as changes may be made in the form, location and relative arrangement of the several parts of the invention and in the sequence of the various method steps Without departing from the principles of the invention, it Will be understood that the invention is not to be limited excepting by the scope of the appended claims.

I claim:

1. An apparatus including an air compressor having a high and low pressure stage, a first heat exchanger comprising hot air conducting means through which air to be cooled flows, and cool air conducting means through which cooling air flows, first conduit means communicating with said low and high pressure stages and said hot air conducting means, a second heat exchanger comprising a hot air flow path and a cooling liquid flow path, means for supplying cooling liquid flow "path, and second conduit means communicating with said high pressure stage and air flow path of said second heat exchanger and said cool air conducting means of said first heat exchanger.

2. An apparatus including an air compressor having a high and low pressure stage, a first heat exchanger with hot air conducting means through which air to be cooled flows and other air conducting means disposed in indirect heat exchange relationshipwith said hot air conducting means, first conduit means in communication with the discharge side of said low pressure stage, the intake side of said high pressure stage and said hot air conducting means for cooling air from said low pressure stage before it enters said high pressure stage, a second heat exchanger comprising a hot air flow path means and cooling water flow path means therein disposed in indirect heat exchange relationship with said hot air flow path means, cooling water supply means in communication with said cooling water flow path, and second conduit means communicating with the discharge side of said high pressure stage and hot air flow path means and said other 'air conducting means of said first exchanger.

3. Anrapparatus including an air compressor with a high and'low pressure cylinder, a heat exchanger comprising a tube bundle and shell section, a first conduit communicating with the discharge side of said lowpressure cylinder and one end of the tube bundle for passing hot air therethrough to be cooled, a second conduit in communication'withthe opposite end of said tube bundle and the intake side of said high pressure cylinder for flowing cooled air thereto, another heat exchanger having a cooling water side and a hot air flow path side, cooling water supply means in communication with said water side for cooling air flowed through the hot air side, a third conduit connected to the discharge of said high pressure cylinder and one end of said hot air flow path, and a fourth conduit connected to the other end of said hot air flow path and the shell side of said heat exchanger whereby air from said high pressure cylinder is cooled to condense moisture therein and thereafter is reheated to cool air passing between the cylinders of said compressor.

4. The apparatus of claim 3 wherein said another heat exchanger comprises a shell with a tube bundle therein, and cooling water flows around said tubes.

'5. The apparatus of claim 1 wherein a third heat exchanger is disposed in said second conduit means between said high pressure stage and said second heat exchanger, and means are provided for supplying cooling water to said third heat exchanger and cool air flow path means therein are disposed therein in communication with said second conduit means.

6. The method of cooling air flowing from the low pressure stage of an air compressor to the high pressure stage to decrease its physical volume and utilizing the heat of said air to reheat cooled air from the high pressure stage comprising the steps of fiowing air from the high pressure stage through an aitercooler, thereafter flowing said cooled air in heat exchange relationship with hot air discharged from the low pressure stage, and thereafter flowing said air from the low pressure stage to the high pressure stage.

7. The method of claim 6 wherein said cooled air flowing from said low pressure stage is cooled a second time, after it is passed in heat exchange relationship with cooled air from said high pressure stage.

8. An apparatus including an air compressor having a high and a low pressure cylinder, each of said cylinders including an inlet and an outlet, a heat exchanger having first and second flow paths defined therewithin, each of said flow paths having an inlet and anoutlet, first conduit means providing communication between the outlet of said low pressure cylinder andthe inlet of the first flow path through said heat exchanger, second conduit means providing communication between the outlet of said first flow path through said heat exchanger and the inlet of said high pressure cylinder, a second heat exchanger, said second heat exchanger having first and second fiow paths defined therewithin, each of said flow paths defined with said second heat exchanger having an inlet and an outlet, third conduit means providing communication between the outlet of said high pressure cylinder and the inlet of the first flow path through said second heat exchanger, fourth conduit means providing communication between the outlet of said first flow path through said second heat exchanger and the inlet of the second flow path of said first heat exchanger, means connected with the inlet and outlet of the second flow path through said heat exchanger for circulating a cooling medium therethrough, the inlet to said low pressure cylinder comprising the inlet of the apparatus and the outlet of the second flow'path through said first heat exchanger comprising the outlet from the apparatus, and means for removing condensed liquid which is condensed in each of said heat exchangers.

References tilted in the file of this patent UNITED STATESPATENTS Germany Aug. 12, 1922 

1. AN APPARATUS INCLUDING AN AIR COMPRESSOR HAVING A HIGH AND LOW PRESSURE STAGE, A FIRST HEAT EXCHANGER COMPRISING HOT AIR CONDUCTING MEANS THROUGH WHICH AIR TO BE COOLED FLOWS, AND COOL AIR CONDUCTING MEANS THROUGH WHICH COOLING AIR FLOWS, FIRST CONDUIT MEANS COMMUNICATING WITH SAID LOW AND HIGH PRESSURE STAGES AND SAID HOT AIR CONDUCTING MEANS, A SECOND HEAT EXCHANGER COMPRISING A HOT AIR FLOW PATH AND A COOLING LIQUID FLOW PATH, MEAN FOR SUPPLYING COOLING LIQUID FLOW PATH, AND SECOND CONDUIT MEANS COMMUNICATING WITH SAID HIGH PRESSURE STAGE AND AIR FLOW PATH OF SAID SECOND 